The Localizing Value Of Focal Delta Slowing In Temporal Lobe Epilepsy

Background Clinical and structural correlates of lateralized interictal delta activity in patients with temporal lobe epilepsy (TLE) have been well documented in the literature. Nevertheless, its occurrence has not been considered a significant clinical feature. Objective To evaluate the significance of focal delta- range slowing for localizing the epileptogenic focus in patients with TLE, and predicting the outcome of temporal lobe surgery. Methods Sixteen consecutive patients with temporal lobe epilepsy who underwent anterior temporal lobe resections were selected for the study. Findings of MRI, SPECT, neuropyschology assessment, pathology and surgical outcome were analyzed and correlated with focal delta slow activity of background rhythm. Results Twelve of 16 patients (75%) had localized temporal delta slowing corresponding to the resection site and pathology. Temporal delta slowing was the most frequent interictal EEG finding (75%) compared to spike and sharp wave (44%). MRI showed concordant abnormalities in 75% of the patients, and neuropyschology testing was able to lateralize the involved hemisphere in 37.5%. SPECT was concordant in 56%. There was no false localization with temporal delta activity. Slow wave EEG had a higher marginal probability than neuropsychological assessment of predicting the focus, and was equally effective as other investigative methods. Conclusion These results suggest that focal temporal delta slowing is useful in the localization of epileptogenic foci. There was no discordance with the resection site and pathology. Introduction Les correlations entre clinique, et topographie des ondes delta intercritiques au cours de l\'epilepsie temporal (TLE) ont ete bien documentees dans la litterature. But Evaluer la relation entre ralentissement delta et la localisation d\'un foyer epileptogene dans le cadre d\'une TLE et apres une lobectomie temporale. Methodes Seize patients consecutifs atteints d\'une epilepsie temporale qui ont beneficie d\'une lobectomie temporale ont ete seletionnes. Les donnees IRM, SPECT, neuropsychologiques, neuropathologiques et l\'evolution post-chirurgicale ont ete analysees et correlees au foyer d\'ondes delta. Resultats Douze des 16 patients (75%) avaient une correspondance entre les ondes delta, et la resection chirurgicale et l\'anatomopathologie. Les ondes lentes delta temporales sont les anomalies les plus frequemment rencontrees durant les periodes intercriques comparees aux spikes et pointes ondes (44%). La concordance entre l\'IRM et les anomalies est notee chez 75% des patients ; les tests neuropsychologiques sont capables de determiner la lateralisation de l\'hemisphere implique dans 37% des cas. La SPECT etait concordante dans 56% des cas. Il n\'y avait pas de faux positif dans la localisation par l\'activite temporale delta. Les ondes EEG lentes ont une plus grande probabilite localisatrice que les tests neuropsychologiques et sont aussi effectives que les autres methodes Conclusion Ces resultats suggerent que les ondes lentes temporales sont utiles dans la localization d\'un foyer epileptique. Il n\'y a aucune discordance entre le site de la resection et l\'anatomo-pathologie. Keywords : EEG, Epilepsie, Crises epileptiques, Chirurgie. Lobe temporal, slowing, EEG, Epilepsy, Seizure, Surgery,Temporal lobe African Journal of Neurological Sciences Vol. 24 (1) 2005: pp. 37-43